N = int(input())

c = input()

l = len(c)
a = 0
b = 0

for i in range(l):
    if c[i] == "R":
        a += 1

for i in range(a, l):
    if c[i] == "R":
        b += 1

print(b) N = int(input()) N int(input()) int input() input c = input() c input() input l = len(c) l len(c) len c a = 0 a 0 b = 0 b 0 for i in range(l):
    if c[i] == "R":
        a += 1 i range(l) range l if c[i] == "R":
        a += 1 c[i] == "R" c[i] c i "R" a += 1 a 1 for i in range(a, l):
    if c[i] == "R":
        b += 1 i range(a, l) range a l if c[i] == "R":
        b += 1 c[i] == "R" c[i] c i "R" b += 1 b 1 print(b) print b b += 1 1 b N = int(input()) int(input()) N b = 0 0 b l = len(c) len(c) l a = 0 0 a a += 1 1 a c = input() input() c
N = int(input())

c = input()

l = len(c)
a = 0
b = 0

for i in range(l):
    if c[i] == "R":
        a += 1

for i in range(a, l):
    if c[i] == "R":
        b += 1

print(b)